1. Combine first 7 ingredients in a large bowl and shape the mixture into balls, about 2 tablespoons each.
2. If you have a toaster oven, (it’s not worth heating the big oven), bake the meatballs for 10 minutes or so to form a crust. This makes the meatballs less likely to break apart while you brown them.
3. Brown the meatballs in a large oil filmed skillet over medium heat. It is not necessary to fully cook them at this point.
4. Add the marinara and reduce the heat to low. Stir gently to coat the meatballs, then cover.
5. Cook 20 minutes, stirring occasionally. The meatballs should be hot and fully cooked.
6. Spread the insides of the sub rolls with the softened butter and sprinkle lightly with the garlic salt. Toast under the broiler until lightly browned, then lay on the cheese, cutting to fit.
7. Divide the meatballs among the sub rolls and top with extra marinara as desired.